"Grimm": Sam Witwer, who plays the vampire Aidan on Syfy's "Being Human," guest stars on tonight's episode, titled "The Show Must Go On." A traveling carnival comes to Portland, and Monroe (Silas Weir Mitchell) and Rosalee (Bree Turner) are called upon to look into some suspicious activities going on there.

"Real Time with Bill Maher": Documentary filmmaker Errol Morris is the interview guest at the beginning of the show. Shane Smith, CEO of the Vice media empire, is the mid-show guest. And the roundtable guests are historian Simon Schama, forner FDIC chair Sheila Bair, and Minn. Rep. Keith Ellison. (10 p.m. HBO)

"Vice": Speaking of Shane Smith, he appears in this episode, visiting Dagestan to look into alleged links to terrorism and the case of suspected Boston Marathon bomber Tamerlan Tsarnaev. Also on tap is a report about the evangelical movement in America's support for Israel. (11 p.m. HBO)